Mitochondrial disease associated with complex I (NADH-CoQ oxidoreductase) deficiency.

Mitochondrial diseases due to a reduced capacity for oxidative phosphorylation were first identified more than 20 years ago, and their incidence is now recognized to be quite significant. In a large proportion of cases the problem can be traced to a complex I (NADH-CoQ oxidoreductase) deficiency (Phenotype MIM #252010). Because the complex consists of 44 subunits, there are many potential targets for pathogenic mutations, both on the nuclear and mitochondrial genomes. Surprisingly, however, almost half of the complex I deficiencies are due to defects in as yet unidentified genes that encode proteins other than the structural proteins of the complex. This review attempts to summarize what we know about the molecular basis of complex I deficiencies: mutations in the known structural genes, and mutations in an increasing number of genes encoding "assembly factors", that is, proteins required for the biogenesis of a functional complex I that are not found in the final complex I. More such genes must be identified before definitive genetic counselling can be applied in all cases of affected families

First-principles studies of kinetics in epitaxial growth of III-V semiconductors

We demonstrate how first-principles calculations using density-functional theory (DFT) can be applied to gain insight into the molecular processes that rule the physics of materials processing. Specifically, we study the molecular beam epitaxy (MBE) of arsenic compound semiconductors. For homoepitaxy of GaAs on GaAs(001), a growth model is presented that builds on results of DFT calculations for molecular processes on the beta2-reconstructed GaAs(001) surface, including adsorption, desorption, surface diffusion and nucleation. Kinetic Monte Carlo simulations on the basis of the calculated energetics enable us to model MBE growth of GaAs from beams of Ga and As_2 in atomistic detail. The simulations show that island nucleation is controlled by the reaction of As_2 molecules with Ga adatoms on the surface. The analysis reveals that the scaling laws of standard nucleation theory for the island density as a function of growth temperature are not applicable to GaAs epitaxy. We also discuss heteroepitaxy of InAs on GaAs(001), and report first-principles DFT calculations for In diffusion on the strained GaAs substrate. In particular we address the effect of heteroepitaxial strain on the growth kinetics of coherently strained InAs islands. The strain field around an island is found to cause a slowing-down of material transport from the substrate towards the island and thus helps to achieve more homogeneous island sizes.Comment: 12 pages, 7 figures, REVTeX, Final version to appear in Appl. Phys. A (2002). Other related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

The Equilibrium Shape of Quantum Dots

The formation of dislocation-free three-dimensional islands during the heteroepitaxial growth of lattice-mismatched materials has been observed experimentally for several material systems. The equilibrium shape of the islands is governed by the competition between the surface energy and the elastic relaxation energy of the islands as compared to the uniform strained film. As an exemplification we consider the experimentally intensively investigated growth of InAs quantum dots on a GaAs(001) substrate, deriving the equilibrium shape as a function of island volume. For this purpose InAs surface energies have been calculated within density-functional theory, and a continuum approach has been applied to compute the elastic relaxation energies.Comment: 10 pages, 4 figures. Submitted to Nuovo Cimento (November 27, 1996)

Effect of the cluster size in modeling the H_2 desorption and dissociative adsorption on Si(001)

Three different clusters, Si_9H_12, Si_15H_16, and Si_21H_20, are used in density-functional theory calculations in conjunction with ab initio pseudopotentials to study how the energetics of H_2 dissociativ e adsorption on and associative desorption from Si(001) depends on the cluster size. The results are compared to five-layer slab calculations using the same pseudopotentials and high qu ality plane-wave basis set. Several exchange-correlation functionals are employed. Our analysis suggests that the smaller clusters generally overestimate the activation barriers and reaction energy. The Si_21H_20 cluster, however, is found to predict reaction energetics, with E_{a}^{des}=56 +- 3 kcal/mol (2.4 +- 0.1 eV), reasonably close (though still different) to that obtained from the slab calculations. Differences in the calculated activation energies are discussed in relation to the efficiency of clusters to describe the properties of the clean Si(001)-2x1 surface.Comment: 10 pages, 6 figures, submitted to J. Chem. Phy

(The Markan and Matthean) Jesus’ appropriation and criticism of the Torah: The question of divorce

According to the Gospel of Matthew, Jesus functions as a Moses figure who, in the Sermon on the Mount, gave the new law of the kingdom of God. In this article it is argued that Jesus drew his ethic from his Jewish tradition, as manifested particularly in the Pentateuch. However, although being an inspiring source, to Jesus the Pentateuch (or scripture) was not an authority that could not be challenged or criticised. This is illustrated by focusing on the question of divorce (Mk 10:2–12; Mt 5:27–32; 19:3–12). It is argued that Jesus’ use of the Pentateuch was guided by an ethic of compassion. In view of Jesus’ stance, an uncritical use of the Bible (as manifested for example in many Christian circles) ironically contradicts the Bible’s own message and nature

Renormalized Second-order Perturbation Theory for The Electron Correlation Energy: Concept, Implementation, and Benchmarks

We present a renormalized second-order perturbation theory (rPT2), based on a Kohn-Sham (KS) reference state, for the electron correlation energy that includes the random-phase approximation (RPA), second-order screened exchange (SOSEX), and renormalized single excitations (rSE). These three terms all involve a summation of certain types of diagrams to infinite order, and can be viewed as "renormalization" of the 2nd-order direct, exchange, and single excitation (SE) terms of Rayleigh-Schr\"odinger perturbation theory based on an KS reference. In this work we establish the concept of rPT2 and present the numerical details of our SOSEX and rSE implementations. A preliminary version of rPT2, in which the renormalized SE (rSE) contribution was treated approximately, has already been benchmarked for molecular atomization energies and chemical reaction barrier heights and shows a well balanced performance [Paier et al, New J. Phys. 14, 043002 (2012)]. In this work, we present a refined version of rPT2, in which we evaluate the rSE series of diagrams rigorously. We then extend the benchmark studies to non-covalent interactions, including the rare-gas dimers, and the S22 and S66 test sets. Despite some remaining shortcomings, we conclude that rPT2 gives an overall satisfactory performance across different chemical environments, and is a promising step towards a generally applicable electronic structure approach.Comment: 16 pages, 11 figure

Assembling Complex I with ACAD9

Acyl-Co dehydrogenase 9 (ACAD9) was thought to play a role in fatty acid oxidation. Nouws et al. (2010) reveal a novel and essential role for this enzyme in mitochondrial complex I assembly. A mutation in ACAD9 causes an isolated complex I deficiency in a subset of patients with mitochondrial disease

Novel Reconstruction mechanisms: A comparison between group-III-nitrides and "traditional" III-V-semiconductors

We have studied the driving forces governing reconstructions on polar GaN surfaces employing first-principles total-energy calculations. Our results reveal properties not observed for other semiconductors, as for example a strong tendency to stabilize Ga-rich surfaces. This mechanism is shown to have important consequences on various surface properties: Novel and hitherto unexpected structures are stable, surfaces may become metallic although GaN is a wide-bandgap semiconductor, and the surface energy is significantly higher than for other semiconductors. We explain these features in terms of the small lattice constant of GaN and the unique bond strength of nitrogen molecules.Comment: 13 pages, 5 figure